The invention refers to a method for pulverizing at least a jet of a liquid material preferrably molten and an apparatus for performing the method.
According to prior art known devices disclosed in German applications 3112339, 3112340, 3518646 and German petty patent 8807489 provide an ultrasonic generator to vibrate a flexible electrode. A liquid applied to the electrode is thus nebulized.
According to German patent 2656330 and 2842232 a standing ultrasonic field is generated between an ultrasonic actuator and a reflector. Molten metal emerging from a melting container is pulverized in the ultrasonic field. The ultrasonic capacity obtained by the known devices is rather limited. Further, the relatively small ultrasonic power in pulverizing leads to a low quenching rate of the molten metal after pulverizing resulting in granular sizes and characteristics to be avoided.
A principal object of the invention is, therefore, to provide a method and an apparatus for increasing the pulverizing capacity. It is a further object to provide an improved quenching of the metallic particles pulverized.
In the present invention the higher energy transfer from the ultrasonic field to the particles to be pulverized is accomplished by generating the ultrasonic field in a pressurized fluid. The pulverizing power is substantially increased by the higher energy density of the ultrasonic field. In addition the metallic particles pulverized are more rapidly quenched in the ultrasonic field of higher energy since they receive a larger impulse or impetus resulting in a "slip" between the fluid and the high speed-metallic particles.
According to a further aspect of the present invention the particles pulverized are compacted immediately after pulverizing and quenching to manufacture a workpiece. To accomplish this metallic particles having super plastic characteristics after being quenched are blasted onto a substrate on which the individual particles are welded together. The blasting takes place preferably under pressure. Compacting is preferrably accomplished when the particles have obtained a stable state after being pulverized and are quenched so far that the microstructure is not changed anymore, but the particles are still hot enough for welding.
According to a principal aspect of the present invention the ultrasonic field is generated in the space between at least a pair of ultrasonic actuators. To further increase the pulverizing capacity, further pairs of actuators may be provided to generate an ultrasonic field having one or more nodal areas. The molten metal is preferrably directed through at least one of said nodal areas, greatly increasing the pulverizing capacity by the superimposing of the ultrasonic fields generated by said pairs of actuators.
Further another aspect of this invention will be more readily apparent when the following specification is reas in conjunction with the accompanying drawings.